1. Field of the Invention
The present invention relates to an electronic component package, and more particularly to a package for surface-mounted components which carries the components to-be-surface-mounted, for example, general semiconductor components or digital IC's, on the upper face side thereof and which is installed on another circuit board or the like by conductor pins protruding from the lower side thereof.
2. Description of the Prior Art
Owing to the advancement of electronics in recent years, the density of integration of electronic components such as so-called semiconductor elements has become very high. It is only natural that the demand for high-density packaging for the higher density electronic components has increased. In order to cope with the high-density packaging of the electronic components various packaging techniques have been developed. However, in actuality packaging techniques capable of satisfactorily meeting the increased density of the electronic components is still in the course of development. In other words, high-density packaging technology is still behind the ever increasing densities in electronic components. In particular, recent electronic components have come to include large numbers of connection terminals and surface-mounting and packaging techniques employing conductor pins have been developed for coping with the large numbers of terminals.
As seen from, for example, Japanese Patent Application Laid-open No. 59-195850, there is a surface-mounting technique wherein an electronic component is received in a cap, with its connection terminals protruding from the side faces of the cap. The positions of the connection terminals correspond to patterns on a printed circuit board. The connection terminals of the electronic component are then directly connected to the patterns with solder or the like as they are placed on contact portions formed on the board. Thus, this surface-mounting technique has the advantages that the electronic component itself can be flatter and the board need not be subjected to any complicated working steps, e.g., the formation of contact holes for the electronic component. On the other hand, as a packaging technique employing conductor pins, there is, for example, the technique as seen in Japanese Patent Application Laid-open No. 60-241244. According to that publication patterns to be electrically connected to the individual conductor pins are formed so as to be concentrated around the electronic components to be packaged. This technique is suited to the packaging of electronic components which are small in size and which require protection such as resin encapsulation.
However, along with the merits of surface-mounted techniques, mentioned above, it is usually difficult to form external connection portions directly under a component to be surface-mounted. The reason is that the conductor circuit is covered by the surface-mounted components. As a result, the side under the surface-mounted component becomes, in effect, difficult to use. Accordingly, with this surface-mounting technique alone, it is difficult to achieve the high-density packaging explained before. Also, the mounting technique employing conductor pins is usually realized with a so-called pin-grid array, with the number of conductor pins equal to the number of terminals of the electronic component which is to be mounted. This equality makes it difficult to simultaneously mount a plurality of electronic components on the same pin-grid array. In particular, the conventional pin-grid array is commonly formed with a conductor circuit and conductor pins suitable for a single electronic component which is to be carried on the array. It can be readily understood, accordingly, that the pin-grid array suffices for packaging a specified electronic component, but that it is not versatile. In other words, conventional pin-grid arrays were designed and fabricated for the particular electronic component to be mounted, and the fabrication of the pin-grid arrays required a large amount of labor and much expense.
Further, so-called programmable IC's which can be programmed after mounting have recently been developed as a component that can be surface-mounted. Programmable IC's are of very high utility because circuits can be freely formed therein. However, a packaging circuit is necessary for a programmable IC, and by choosing a particular packaging circuit, the use of a programmable IC may be limited. In this regard, it would be very convenient if the packaging circuit could also be freely changed even after the corresponding programmable IC was mounted.